17,447 research outputs found
Complex network statistics to the design of fire breaks for the control of fire spreading
A computational approach for identifying efficient fuel breaks partitions for the containment of fire incidents in forests is proposed. The approach is based on the complex networks statistics, namely the centrality measures and cellular automata modeling. The efficiency of various centrality statistics, such as betweenness, closeness, Bonacich and eigenvalue centrality to select fuel breaks partitions vs. the random-based distribution is demonstrated. Two examples of increasing complexity are considered: (a) an artificial forest of randomly distributed density of vegetation, and (b) a patch from the area of Vesuvio, National Park of Campania, Italy. Both cases assume flat terrain and single type of vegetation. Simulation results over an ensemble of lattice realizations and runs show that the proposed approach appears very promising as it produces statistically significant better outcomes when compared to the random distribution approach
Strong Magnetic Limit of String Theory
We show that there exists a certain limit in type I and type II superstring
theory in the presence of a suitable configuration of magnetic U(1) fields
where all string excitations get an infinite mass, except for the neutral
massless sector and for the boson and fermion string states lying on the
leading Regge trajectory. For a supersymmetric configuration of magnetic fields
in internal directions, the resulting theory after the limit is a 3+1 Lorentz
invariant supersymmetric theory. Supersymmetry can be broken by introducing
extra components of the magnetic field or else by finite temperature. In both
cases we compute the one-loop partition function for the type I string model
after taking the limit, which turns out to be different from the Yang-Mills
result that arises by a direct limit. In the case of finite
temperature, no Hagedorn transition appears, in consistency with the reduction
of the string spectrum. In type II superstring theory, the analogous limit is
constructed by starting with a configuration of Melvin twists in two or more
complex planes. The resulting theory contains gravitation plus an infinite
number of states of the leading Regge trajectory.Comment: 10 pages. Minor correction
Use of phytotherapics in dogs and cats.
Phytotherapy is one of the most utilized non conventional medicines (NCM) both in human and veterinary medicine. It can be used to mitigate and prevent slight diseases and to support conventional medicine using allopathic drugs. In this paper the Authors report the phytoterapeutics most utilized in both dogs and cats, in which the use of phytotherapics is increasing, despite the prejudices of the academic world and of the veterinary practitioners. Laws regarding the use of non conventional medicines in veterinary practises are lacking in Italy, despite many other countries in Europe; yet National Federation of Italian Veterinaries (F.N.O.V.I.) asserted that the use of NCM has to be considered a veterinary practise at all. At the end of this paper, the Authors provided many examples of phytotheapic prescriptions to control different illness in both dogs and cats
Conformal Field Theory for the Superstring in a Ramond-Ramond Plane Wave Background
A quantizable worldsheet action is constructed for the superstring in a
supersymmetric plane wave background with Ramond-Ramond flux. The action is
manifestly invariant under all isometries of the background and is an exact
worldsheet conformal field theory.Comment: 13 pages harvma
Body image perception and body composition: assessment of perception inconsistency by a new index
BACKGROUND: A correct perception of the body image, as defined by comparison with actual anthropometric analyses, is crucial to ensure the best possible nutritional status of each individual. Bioimpedance analysis (BIA) represents a leading technique to assess body composition parameters and, in particular, the fat mass. This study examined the self-perception of body image at various levels of adiposity proposing a new index. METHODS: We investigated 487 young Italian adults (mean age of males: 21.9 ± 2.4 years; mean age of females: 21.0 ± 2.2 years). Each subject could choose, on the Contour Drawing Rating Scale, the silhouette that he/she considered most resembling his/her perceived body image as well as his/her ideal body image. On each subject, we performed anthropometric measurements and determined the values of Fat mass and út with BIA. A new index, FAIFAT (Feel fat status minus Actual fat status Inconsistency), was developed to evaluate possible fat status perception inconsistencies by BIA. RESULTS: Based on ideal and feel body image comparison, women showed higher dissatisfaction than men and preferred slimmer silhouettes. FAIFAT values indicated that the fat status perception was correct in the majority of the examined individuals and only three subjects showed a serious misperception. CONCLUSIONS: Our findings suggest that FAIFAT is an appropriate index for assessing the perceived fat status from the body image when compared with data obtained by BIA. In a population, the use of this index will allow the correct identification of groups at risk for eating disorders
Bias-dependent Contact Resistance in Rubrene Single-Crystal Field-Effect Transistors
We report a systematic study of the bias-dependent contact resistance in
rubrene single-crystal field-effect transistors with Ni, Co, Cu, Au, and Pt
electrodes. We show that the reproducibility in the values of contact
resistance strongly depends on the metal, ranging from a factor of two for Ni
to more than three orders of magnitude for Au. Surprisingly, FETs with Ni, Co,
and Cu contacts exhibits an unexpected reproducibility of the bias-dependent
differential conductance of the contacts, once this has been normalized to the
value measured at zero bias. This reproducibility may enable the study of
microscopic carrier injection processes into organic semiconductors.Comment: 4 pages, 4 figure
Non-Commutative Yang-Mills and the AdS/CFT Correspondence
We study the non-commutative supersymmetric Yang-Mills theory at strong
coupling using the AdS/CFT correspondence. The supergravity description and the
UV/IR relation confirms the expectation that the non-commutativity affects the
ultra-violet but not the infra-red of the Yang-Mills dynamics. We show that the
supergravity solution dual to the non-commutative N=4 SYM in four dimensions
has no boundary and defines a minimal scale. We also show that the relation
between the B field and the scale of non-commutativity is corrected at large
coupling and determine its dependence on the 't Hooft coupling \lambda.Comment: 9 pages, 1 figure, References and comments added, typos correcte
On the Prior Sensitivity of Thompson Sampling
The empirically successful Thompson Sampling algorithm for stochastic bandits
has drawn much interest in understanding its theoretical properties. One
important benefit of the algorithm is that it allows domain knowledge to be
conveniently encoded as a prior distribution to balance exploration and
exploitation more effectively. While it is generally believed that the
algorithm's regret is low (high) when the prior is good (bad), little is known
about the exact dependence. In this paper, we fully characterize the
algorithm's worst-case dependence of regret on the choice of prior, focusing on
a special yet representative case. These results also provide insights into the
general sensitivity of the algorithm to the choice of priors. In particular,
with being the prior probability mass of the true reward-generating model,
we prove and regret upper bounds for the
bad- and good-prior cases, respectively, as well as \emph{matching} lower
bounds. Our proofs rely on the discovery of a fundamental property of Thompson
Sampling and make heavy use of martingale theory, both of which appear novel in
the literature, to the best of our knowledge.Comment: Appears in the 27th International Conference on Algorithmic Learning
Theory (ALT), 201
Conformal description of horizon's states
The existence of black hole horizon is considered as a boundary condition to
be imposed on the fluctuating metrics. The coordinate invariant form of the
condition for class of spherically symmetric metrics is formulated. The
diffeomorphisms preserving this condition act in (arbitrary small) vicinity of
the horizon and form the group of conformal transformations of two-dimensional
space ( sector of the total space-time). The corresponding algebra
recovered at the horizon is one copy of the Virasoro algebra. For general
relativity in dimensions we find an effective two-dimensional theory
governing the conformal dynamics at the horizon universally for any .
The corresponding Virasoro algebra has central charge proportional to the
Bekenstein-Hawking entropy. Identifying the zero-mode configuration we
calculate . The counting of states of this horizon's conformal field
theory by means of Cardy's formula is in complete agreement with the
Bekenstein-Hawking expression for the entropy of black hole in dimensions.Comment: 13 pages, latex, no figures; the final version to appear in Phys.
Lett.
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